Abstract: A method for separation and determination of nine lanthanides chelates in 12min by using reversed phase ion pair high performance liquid chromatography with 4-(2-pyridylazo) resercinol (PAR) as the chromophoric reagent has been studied. The optimum condition of separation and determination are also described in this paper. The calibration curve is a linear function of concentration in the range of 0. 01 -3. 0 ppm for La, 0. 03-2. 8 ppm for Ce, 0. 06-3. 50 ppm for Nd, 0. 05-3. 8 ppm for Pr, 0. 01 -3. 0 ppm for Sm, 0. 05-3. 40 ppm for Eu, 0. 02-3. 0 ppm for Tb, 0. 01 -3. 4 ppm for Ho and 0. 02-4. 00 ppm for Er. The variational coefficient is found to be less than

Key words: Separation and determination of rare earths, Reversed phase ion pair high performance liquid chromatography, 4-(2-pyridylazo) resercinol